There have been known saccharides, which are composed of glucose molecules as constituent saccharides, such as amyloses, amylodextrins, maltodextrins, maltooligosaccharides, and isomaltooligosaccharides as partial starch hydrolysates. These saccharides are, usually, known to exhibit reducibility and to have reducing and non-reducing groups at their both molecular ends. In general, it has been known that partial starch hydrolysates having a relatively high reducing power on a dry solid basis (d.s.b.) usually have a relatively low molecular weight and viscosity and a relatively high sweetness, and have the demerits that they easily induce the amino carbonyl reaction, for example, with substances having amino groups such as amino acids and proteins to cause browning or unsatisfactory smell and facilitate the quality deterioration. To improve the demerits, there has long been desired a method for lowering or eliminating the reducing power without altering glucose molecules as constituent saccharides of partial starch hydrolysates. For example, as disclosed in Journal of American Chemical Society, Vol. 71, pp. 353–358 (1949), it was reported that a method for forming α-, β-, and γ-cyclodextrins, composed of 6–8 glucose molecules linked together via the α-1,4 glucosidic linkage by contacting starches with an amylase derived from a microorganism of the species Bacillus macerans. Today, these cyclodextrins are produced on an industrial scale and used in diversified fields which need their inherent properties such as non-reducibility, tasteless, and enclosing ability. As disclosed, for example, in Japanese Patent Kokai Nos. 143,876/95 and 213,283/95 applied for by the same applicant as the present invention, there has been known a method for producing trehalose (α,α-trehalose), composed of two glucose molecules linked together via the α,α-linkage, by contacting a non-reducing saccharide-forming enzyme and a trehalose-releasing enzyme with partial starch hydrolysates such as maltooligo-saccharides. At present, trehalose has been industrially produced from starches and used in different fields which need the advantageous non-reducibility, mild- and high quality-sweetness of trehalose. As described above, trehalose having a glucose polymerization degree (DP) of two, and α-, β-, and γ-cyclodextrins having a DP of 6 to 8 are produced on an industrial scale and used in view of their advantageous properties, however, the varieties of non- or low-reducing saccharides are limited, so that more diversified saccharides other than the above-exemplified saccharides are greatly required.
Recently, a new type of cyclotetrasaccharide, composed of glucose units, was reported. European Journal of Biochemistry, Vol. 226, pp. 641–648 (1994) shows that a cyclic tetrasaccharide having the structure of cyclo{→6)-α-D-glucopyranosyl-(1→3)-α-D-glucopyranosyl-(1→6)-α-D-glucopyranosyl-(1→3)-α-D-glucopyranosyl-(1→} (may be called “cyclotetrasaccharide” throughout the specification) is formed by contacting alternanase, a hydrolyzing enzyme, with alternan composed of glucose residues mainly linked together via the α-1,3 and α-1,6 bonds, alternatively, and crystallizing the formed cyclic tetrasaccharide in the presence of methanol as an organic solvent.
Cyclotetrasaccharide has an ability of including compounds based on its cyclic structure and does not cause the amino carbonyl reaction due to its non-reducibility, and therefore it is expected to be processed and used with lesser fear of browning and deterioration. However, the material alternan and alternanase as an enzyme, which are essential for producing the saccharide, are not easily obtainable; and also microorganisms for producing the alternan and alternanase are not easily available.
Under these conditions, the establishment of a novel process for easily producing cyclotetrasaccharide on an industrial scale and the providing of cyclotetrasaccharide with revealed physicochemical properties are greatly expected.